This is a pattern hack of the Sew Sweetness Petrillo Bag. The modification is to make this bag into a convertible backpackl! While this tutorial is free, you’ll need to pick up the Petrillo Bag pattern in order to complete the rest of the bag.
DEFINITION – Pattern Hack [pat-ern hack]: to modify or write a sewing pattern in a skillful or clever way.
For this pattern hack I am going to show you how to modify Sara’s Petrillo Bag strap to turn this into a convertible backpack so you can wear your bag over your shoulder or on your back. I am also going to show you an alternative flap option.
I have only modified the strap and flap so please refer to the original pattern for the supply list and sewing instructions for the rest of the bag pieces.
*** PLEASE NOTE: IF YOU ARE EXTENDING THE FLAP YOU NEED TO ADJUST THE MAGNETIC SNAP PLACEMENT ON YOUR BAG FRONT, SEE BELOW ***
For the strap you will need
- 1/2 yard of fabric
- 1/2 yard of fusible fleece to interface the strap
- 2 x 1 1/2″ rectangle rings
- 2 x 1 1/2″ O rings
- 2 x 1 1/2″ sliders
For the flap you will need
- Exterior fabric piece 14″ x 14″
- Lining fabric piece 14″ x 14″
- magnetic snap
- 2 x shape flex SF101 14″ x 14″
- 1 x soft and stable or foam of your choice 14″ x 14″
Extending the Flap using Sara’s FLAP PATTERN PIECE
- Print and cut TWO flap pattern pieces.
- Stick one of the flap pattern pieces onto a fresh piece of printer paper, matching the bottom right hand corner of the FLAP PATTERN PIECE with the bottom right hand corner of the paper.
- Measure 5 inches up from the top of the original pattern piece and draw a horizontal line across the width of your paper. Cut along this line and discard the paper above it.
- Draw a straight line up from the left edge of the FLAP PATTERN PIECE to the top of the paper.
- Cut out the curve of the bottom edge and up along this line so you have a pattern piece that looks like the photo below.
- Take the SECOND FLAP PATTERN PIECE and place it on top of your new piece, matching the top edges.
- Draw a line along the curve at the top left corner, shown in heavy marker in the picture below.
– Cut along this line to curve the top of the flap pattern piece.
Use your new FLAP PATTERN PIECE to cut
- 1 x flap exterior
- 1 x flap lining
- 1 x soft and stable
- 2 x shape flex
Interfacing your flap fabric
- Iron SF101 onto the wrong side of your flap exterior fabric and flap lining fabric
- zig zag stitch your foam to the wrong side of your flap exterior fabric
Magnetic Snap Placement
- Add a magnetic snap to the FLAP LINING PIECE, centred 1 1/2 ” from the bottom edge
- Add a magnetic snap to the bag front centred 8 3/4″ from the top edge. (THIS IS 5 INCHES LOWER THAN SARA’S ORIGINAL PATTERN INSTRUCTIONS, AS THE FLAP HAS BEEN EXTENDED BY 5 INCHES)
Making Your Bag Strap
There are a few components of the strap
– Rectangle Ring Holders
Cut 2 x Strap Fabric 8″ x 5 3/4″
Cut 2 x fusible fleece 8″ x 3″
- Centre the fusible fleece along the width of each piece
- Fold and iron the long edges down onto the fusible fleece along the length of each piece
- Fold in half lengthwise and iron on both sides to adhere the fusible fleece
- Top stitch along all edges
- Thread your strap through the rectangle ring and fold in half, baste the bottom edge.
– O Ring Holders
Cut 2 x Strap Fabric 6″ x 5 3/4″
Cut 2 x fusible fleece 3″ x 3″
- Centre your fleece onto the wrong side of your O ring holder fabric piece
- Fold and iron the long edges down onto the fleece (as you did with your rectangle ring holders)
- Fold in half lengthwise and iron both sides
- Top stitch along all edges
- Thread the strap through the O ring. Fold the fabric that has no fusible fleece towards the wrong side as in the picture below. Clip in place (do not stitch yet)
Cut 2 x strap fabric 5 3/4″ x width of fabric
Join these pieces together, iron the seam open. Measure the length. Cut enough fusible fleece to make a strip 3″ wide to interface your strap leaving a 1/2″ gap at either end.
- centre the fusible fleece along the length of the strap, leaving 1/2″ uncovered at both ends. Fold the excess fabric on both short sides over onto the fusible fleece and iron down to make a neat edge at the ends of your strap.
- Fold and iron the long edges of your strap onto the fusible fleece
- Fold your strap in half length wise and iron on both sides to adhere the fusible fleece.
- top stitch along all edges.
Attaching the Rectangle Ring Holders to the Bag Back
- Position your folded pieces on the BACK piece, 2 inches from each side, with 2 inches of the fabric strip on the fabric. Baste in place. DO NOT CUT THE EXCESS FABRIC THAT EXTENDS BELOW THE LOWER EDGE
- Sew the bag base onto the bag back as per Sara’s pattern instructions
- Top stitch an X box through the rectangle strap and back fabric to hold the strap in place. Using your X box as a placement guide, sew a rectangle through the base and strap extension piece for extra security.
Attaching the O ring holders to the Bag Sides
- centre the O ring as high as you can onto the bag side piece, making sure you allow enough space to sew the side seams.
- Top stitch an X box, enclosing the raw edges in your stitching.
- Attach the sides to the bag as per Sara’s pattern instructions and follow the rest of the pattern instructions to complete the bag. We will add the strap once the bag is completed.
Attaching the strap
Take a deep breath and go slowly, this stage took me a while to work out 🙂
– Attach a slider to ONE end of the strap, sew in place.
- Place your bag upright with the back facing you. Thread the strap down through the left rectangle ring as shown in the photo below. Please note the position of the rectangle ring with the seam facing towards you.
– Thread the end of the strap back through the rectangle ring
– Thread the strap up along the left side of your bag, through the O ring, over the top of your bag and back down through the right hand O ring
– Thread the strap through your second slider
– Thread the strap up through the right hand rectangle ring
*** DO NOT PASS THE SLIDER THROUGH THIS RECTANGLE RING ***
- Thread the end of the strap through the back of the slider (you may need to loosen the fabric on the slider to do this)
- Sew the end down to the strap (HINT, PIN THIS IN PLACE FIRST TO MAKE SURE YOU HAVE EVERYTHING IN THE RIGHT PLACE)
If you are like me and were holding your breath to concentrate through all those steps you can breathe now. I hope you enjoy your new convertible backpack 🙂